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ECE 261 James Morizio 1
ECE 261: Full Custom VLSI DesignProf. James Morizio
Dept. Electrical and Computer EngineeringHudson HallPh: 201-7759
E-mail: [email protected]: http://www.ee.duke.edu/~jmorizio
Course URL: http://www.ee.duke.edu/~jmorizio/ece261/261.html
ECE 261 James Morizio 2
Course Objectives
• Introduction to CMOS VLSI design methodologies– Emphasis on full-custom design– Circuit and system levels
• Extensive use of Mentor Graphics CAD tools for IC design, simulation, and layout verification
• Specific techniques for designing high-speed, low-power, and easily-testable circuits
ECE 261 James Morizio 3
Designing for VLSI
• Designing a system on a chip– Craft components from silicon rather than selecting catalog parts
• ICs (chips) are batch fabricated– Inexpensive unit cost
• Bugs are hard to fix!– Extensive design verification needed
ECE 261 James Morizio 4
VLSI Design: Overview• VLSI design is system design
– Designing fast inverters is fun, but need knowledge of all aspects of digital design: algorithms, systems, circuits, fabrication, and packaging
– Need to bridge gap between abstract vision of digital design andthe underlying digital circuit and its peculiarities
– Circuit-level optimization, verification, and testing techniques are important
• Tall thin approach does not always work– Today’s designer is “fatter”, but well-versed in both high-level and
low-level design skills
ECE 261 James Morizio 5
VLSI: Enabling Technology
• Automotive electronic systems– A typical Chevrolet has 80 ICs (stereo systems, display panels, fuel
injection systems, smart suspensions, antilock brakes, airbags)
• Signal Processing (DSP chips, data acquisition systems)• Transaction processing (bank ATMs)• PCs, workstations• Medical electronics (artificial eye, implants)• Multimedia
ECE 261 James Morizio 6
Design Complexity• Transistor counts and IC densities continue to
grow!– Moore’s Law-The number of transistors on an IC doubles every
1.5 years– Intel x486: 1 million transistors (1989), PowerPC: 2-3 million
transistors (1994), Pentium: 3.1 million transistors (1994), DECAlpha: 10 million transistors (1995)-9 million in SRAM, Pentium IV (2001): 42 million transistors
• Memory (DRAM) is the “technology driver”– 256 Mbits DRAM now commercially available
ECE 261 James Morizio 7
A Brief History• 1958: First integrated circuit
– Flip-flop using two transistors– Built by Jack Kilby at Texas Instruments
• 2003– Intel Pentium 4 µprocessor (55 million transistors)– 512 Mbit DRAM (> 0.5 billion transistors)
• 53% compound annual growth rate over 45 years– No other technology has grown so fast so long
• Driven by miniaturization of transistors– Smaller is cheaper, faster, lower in power!– Revolutionary effects on society
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Annual Sales
• 1018 transistors manufactured in 2003– 100 million for every human on the planet
0
50
100
150
200
1982 1984 1986 1988 1990 1992 1994 1996 1998 2000 2002
Year
Global S
emiconductor B
illings(B
illions of US
$)
ECE 261 James Morizio 9
VLSI Technology
• CMOS: Complementary Metal Oxide Silicon– Based on voltage-controlled field-effect transistors (FETs)
• Other technologies: bipolar junction transistors (BJTs), BiCMOS, gallium arsenide (GaAs)– BJTs, BiCMOS, ECL circuits are faster but CMOS consumes
lower power and are easier to fabricate– GaAs carriers have higher mobility but high integration levels are
difficult to achieve in GaAs technology
ECE 261 James Morizio 10
Transistor Types
• Bipolar transistors– npn or pnp silicon structure– Small current into very thin base layer controls large currents
between emitter and collector– Base currents limit integration density
• Metal Oxide Semiconductor Field Effect Transistors– nMOS and pMOS MOSFETS– Voltage applied to insulated gate controls current between source
and drain– Low power allows very high integration
ECE 261 James Morizio 11
IC Manufacturing• Some manufacturing processes are tightly coupled to the
product, e.g. Buick/Chevy assembly line• IC manufacturing technology is more versatile• CMOS manufacturing line can make circuits of any type
by changing some basic tools called masks– The same plant can manufacture both microprocessors and microwave
controllers by simply changing masks
• Silicon wafers: raw materials of IC manufacturing
Teststructure Wafer
IC
ECE 261 James Morizio 12
The First Computer
The BabbageDifference Engine(1832)25,000 partscost: £17,470
ECE 261 James Morizio 13
ENIAC - The first electronic computer (1946)
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Invention of the Transistor• Vacuum tubes ruled in first half of 20th century
Large, expensive, power-hungry, unreliable• 1947: first point contact transistor
– John Bardeen and Walter Brattain at Bell Labs– Read Crystal Fire
by Riordan, Hoddeson
ECE 261 James Morizio 15
• 1970’s processes usually had only nMOS transistors– Inexpensive, but consume power while idle– 1980s-present: CMOS processes for low idle power
MOS Integrated Circuits
Intel 1101 256-bit SRAM Intel 4004 4-bit µProc
ECE 261 James Morizio 16
Moore’s Law• 1965: Gordon Moore plotted transistor on each
chip– Fit straight line on semilog scale– Transistor counts have doubled every 26 months
Year
Transistors
40048008
8080
8086
80286Intel386
Intel486Pentium
Pentium ProPentium II
Pentium IIIPentium 4
1,000
10,000
100,000
1,000,000
10,000,000
100,000,000
1,000,000,000
1970 1975 1980 1985 1990 1995 2000
Integration Levels
SSI: 10 gates
MSI: 1000 gates
LSI: 10,000 gates
VLSI: > 10k gates
ECE 261 James Morizio 17
Corollaries• Many other factors grow exponentially
– Ex: clock frequency, processor performance
Year
1
10
100
1,000
10,000
1970 1975 1980 1985 1990 1995 2000 2005
4004
8008
8080
8086
80286
Intel386
Intel486
Pentium
Pentium Pro/II/III
Pentium 4
Clock S
peed (MH
z)
ECE 261 James Morizio 18
Evolution in Complexity
ECE 261 James Morizio 19
Evolution in Transistor Count
ECE 261 James Morizio 20
Evolution in Speed/Performance
ECE 261 James Morizio 21
Intel 4004 Micro-Processor
ECE 261 James Morizio 22
Intel Pentium (II) microprocessor
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Silicon in 2010
Die Area: 2.5x2.5 cmVoltage: 0.6 VTechnology: 0.07 µµµµm
Density Access Time(Gbits/cm2) (ns)
DRAM 8.5 10DRAM (Logic) 2.5 10SRAM (Cache) 0.3 1.5
Density Max. Ave. Power Clock Rate(Mgates/cm2) (W /cm2) (GHz)
Custom 25 54 3Std. Cell 10 27 1.5
Gate Array 5 18 1Single-Mask GA 2.5 12.5 0.7
FPGA 0.4 4.5 0.25
ECE 261 James Morizio 24
Design Abstraction Levels
n+n+S
GD
+
DEVICE
CIRCUIT
GATE
MODULE
SYSTEM
ECE 261 James Morizio 25
New Design Challenges• Interconnect-centric design
– Capacitive coupling, inductance effects, delay modeling• Power densities, power grid design, leakage
– 80 W/cm2 ∼ 100 W/cm2
• Nuclear reactor: 150 W/cm2
– 80% increase in power density per generation (voltage scales by 0.8)
– 225% increase in current density– 1.3V power supply leads to 60W power with 60A
sustained current• 2X the current (surge) in your car’s alternator
• Statistical design (P,V,T)